What is "massive compact halo object"

alt. (context astronomy physics English) Any kind of astronomical body comprising normal baryonic matter that in sufficient numbers might explain the apparent presence of dark matter in galaxy halos. n. (context astronomy physics English) Any kind of astronomical body comprising normal baryonic matter that in sufficient numbers might explain the apparent presence of dark matter in galaxy halos.

Massive astrophysical compact halo object (MACHO) is any kind of astronomical body that might explain the apparent presence of dark matter in galaxy halos. A MACHO is a body composed of normal baryonic matter that emits little or no radiation and drifts through interstellar space unassociated with any planetary system. Since MACHOs are not luminous, they are hard to detect. MACHOs include black holes or neutron stars as well as brown dwarfs and unassociated planets. White dwarfs and very faint red dwarfs have also been proposed as candidate MACHOs. The term was coined by astrophysicist Kim Griest.